Ok to grind brake discs ?

[Philodoxo]

Is it okay to use a grinder on the brake discs to make them look good ? Or do I remove the hardness or make them to thin ?

Back side - before grinding:

Front side - after grinder with sandpaperdisc has been there.

Not all finished, but the better look is almost there.

 

[drewpy]

erm, the surface has to be totally flat which means it has to be done on a lathe.

IMHO at best, you'll have a pulsing front brake when it's applied, at worst it'll lock up

 

[Philodoxo]

Fuck - i didn't think of that.

Thanks for Your friendly way to tell me I'm a complete idiot !

 

[drewpy]

you won't be the first and definitely not the last. depending on how much meat you have (4mm is the wear limit) get them on a lathe

 

[16VGTIDave]

I agree with drewpy.

But, to offer another "shade tree mechanic" option, I've used 400 grit adhesive abrasive disks (the kind that body shops use on their orbital sanders) stuck to the surface of new brake pads, and trimmed to fit.

I installed the pads and drove at slow speeds and repeatedly applied the brakes gently and let the abrasive do it's thing. One has to be careful doing this, as the brakes don't work as expected, and if you get too much heat built up, the adhesive will let go and the paper will slide off the pads.

This will clean up rotors that are glazed, but won't remove enough metal from the rotor to remove deep grooves.

A lathe is the best option, if available...

Dave

 

[Scorpio1963]

My disk is going to have to hit a lathe as it looks even worse than Philodoxo`s

 

[Philodoxo]

I'll start up the old Batignolle lathe. Thanks !

 

[Old Okie]

A lathe probably will not work on these brake disks. The metal is so hard that it will run away from the cutting tool. They can be resurfaced on a milling machine, I have had some done. Cost about $40.00 for both sides and it worked pretty well. My disk is slightly below the minimum thickness but for this bike, a 1982 Honda CX500 Turbo, a new rotor cost about $200.00 so I will live with what I have. I was told that a backing plate could be machined for the rotor and that would make the rotor stiff enough to resurface it with a lathe but that is a lot of trouble.

 

[Scorpio1963]

Old Okie $200 WOW! You mean to tell me that there isnt a cutting tool for lathe that can clean up these disk?

 

[Old Okie]

The problem with doing the rotors on a lathe is, the metal in the rotor is really hard and the rotor is somewhat flexible. When you put the cutting tool to the rotor, the rotor leans way from the tool. I took my rotor to a good machine shop and this was their story. They recommended I take it to a shop that had a flat bed milling machine. The flat bed machine did a good job but not perfect. If the rotor is not nearly perfect you will have pulsing brakes or worse. The rotor I had milled is on the rear and I can tell that is is just barely useable. Probably would not work on the front at all.

 

[drewpy]

just done a quick google about this and whilst its possible using a flywheel re-surfacer to wet grind the discs, the consensus is that if the disk overheats and shatters, due to the thinner material, you'll be off the bike.

its done regularly on cars, in fact there's a mobile lathe that uses the hub to spin the disk and its cut both sides simultaneously.


caveat emptor I think

 

[Scorpio1963]

That puts me in a hell of a predictment cause my rotor is so bad that even turning them on lathe or milling probaly wont help.Guess I`ll be searching on the net for another one or going out to the motorcycle bone yard out by where I live.

 

[Old Okie]

I got lucky on the '78 XS400E I fixed up for a friend, I doubt that the front brake had ever been used but the rear disk/rotor was a total loss. The rear wheel on the bike was bent, I found a wheel at a salvage yard with a very good brake rotor, I guess that was lucky for me. Forum members furnished a lot of parts for this bike and it is alive and well.

 

[Scorpio1963]

On My Bike I rarely use my front brakes only when ladies in minivans turn out in front of me haha.Since its so groved I`ll probaly just leave it alone and rebuild my caliper and put fresh brake pads on since I have nothing left of my old ones.

 

[Old Okie]

I am sure that you can find a rotor somewhere on this forum. The front brake is 70% of your braking, the rear may work but is not enough in an emergency. I believe that the rotor from several models will fit these bikes. I would hate for you to get hurt because the bike had none or a poor front brake.

What a drag it is getting old, I agree, turned 75 in October.

 

[Scorpio1963]

I am sure that you can find a rotor somewhere on this forum. The front brake is 70% of your braking, the rear may work but is not enough in an emergency. I believe that the rotor from several models will fit these bikes. I would hate for you to get hurt because the bike had none or a poor front brake.

What a drag it is getting old, I agree, turned 75 in October.

Well before my calipers started locking up on me the front brakes work very well,a little bit too well on my gravel road

Old Okie I say you definately went over the hump at 75 but be blessed you have had 75 years of life to enjoy .BTW I lived in Tulsa for about 22 years off and on and my children still live down around the area.

 

[JPaganel]

I was googling on the subject and found these guys: http://www.truedisk.net/

I haven't used them, but they sound like they know what they are talking about.

 

[Old Okie]

I am about 100 miles or so from Tulsa, my son and his family live in south Tulsa,just east of the river and south of the new turnpike.

I would say I have had a good 75 years, I am fat, sassy and fairly healthy. We have raised 4 kids who are doing well. I am not as strong as I was and riding is getting harder for me. If I drop my bike I may not be able to set it back up. Another year or so.....

 

[Scorpio1963]

Anyways I`ll be looking into brake issues over winter by the time riding season comes back around I should be good to go.